1. Field of the Invention
Aspects of the present invention relate to an image forming apparatus and a control method thereof.
2. Description of the Related Art
One example of an image forming apparatus is an electro-photographic image forming apparatus, wherein a photoconductor that is charged by a charge device is exposed to light emitted from a Laser Scanning Unit (LSU), according to a print signal, such that an electrostatic latent image is formed on the surface of the photoconductor. The electrostatic latent image is developed by a developer fed from a developing device, to form an image, and then the image is transferred to paper, using a transfer device, completing a desired image.
In the above-described image forming apparatus, the developer is composed of a powdered toner and a liquid-phase carrier. The toner is attached to the electrostatic latent image, to change the electrostatic latent image into a toner image. Some of the toner attached to the electrostatic latent image is not transferred from the photoconductor to the transfer device, or from the transfer device to the paper, and instead remains on the photoconductor or the transfer device.
The toner residue on the photoconductor and transfer device is removed by a cleaning device and is stored in a waste toner container, via the operation of a waste toner collecting device. Meanwhile, the liquid-phase carrier is recovered by a carrier collecting device.
In a color developing device yellow, cyan, magenta, and black toners are generally used. This kind of color developing device generates a greater amount of waste toner than a developing device using only one toner. Accordingly, it is necessary to sense whether the waste toner container is full of waste toner, in order to know an exchange time of the waste toner container.
Conventionally, a waste toner sensing device is provided in the image forming apparatus, which includes a light emitting element to emit light and a light receiving element to receive the light emitted from the light emitting element, which are arranged on opposing sides of the waste toner container. The light emitting element includes a light emitting diode, and the light receiving element includes a semiconductor switch device. If the light emitted from the light emitting element collides with the waste toner in the waste toner container, the light receiving element will fail to receive the light. In this way, sensing the presence of waste toner is possible, by determining how much of the light is absorbed/blocked by the waste toner. In this case, it will be appreciated that the smaller the quantity of light received by the light receiving element, the greater the amount of waste toner in the waste toner.
Conventionally, a maximum current allowed by the light emitting diode is applied to the light emitting element, to allow the light emitting element to emit a maximum quantity of light. This is to enable the light to pass through the waste toner container, even when an inner surface of the waste toner container is contaminated. However, applying the maximum current to the light emitting element may shorten the lifespan of the light emitting element and the waste toner sensing device, and may waste of energy.